The present invention generally relates to a semiconductor apparatus, and in particular, the present invention relates to a semiconductor apparatus with self-security function, which protects restricted data stored therein.
An IC (Integrated Circuit) may include a memory, which stored restricted data, and circuitry designed by using confidential technique or know-how. It is required to prevent such important information and technique from being analyzed or stolen by rogues. Conventionally, an IC is covered with a protection film (passivation film), so that the variation of capacity occurs when such a film is taken out in an unauthorized manner. When the variation of capacity occurs, the IC is invalidated and rogues can not analyze the restricted data stored therein.
According to the conventional technique, however, the protection film is usually transparent; therefore, it is easy to recognize the circuitry in the IC using a microscope or the like. If functional blocks arranged in the IC are discriminated, the protection film would be removed using an ion-beam device or the like without making capacity variation in the IC. As a result, the function of the circuitry can be analyzed by probing technique.
Accordingly, an object of the present invention is to provide a semiconductor apparatus in which the function of the circuitry is prevented from being stolen or analyzed.
Additional objects, advantages and novel features of the present invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
According to a generic aspect of the present invention, a semiconductor apparatus includes a functional block that performs necessary functions for the proper operation; a functional signal line that is connected to the functional block to transmit a functional signal; and an enable signal line to supply an enable signal to the functional block. The enable signal line includes a part that is formed on an upper layer of the functional signal line.
The enable signal line is formed on a layer that is upper than a layer, on which the functional signal line is formed, so that the functional signal line would easily be broken at the same time when rogues remove the enable signal line and the functional block is invalidated. As a result, the functional block is prevented from being analyzed by rogues in an unauthorized manner.
Preferably, such a semiconductor apparatus further includes an opaque layer (not transparent), which is formed over the functional signal line, to cover up the functional signal line. The functional signal line is covered with the opaque layer, so that it is difficult to recognize the location of the functional signal line; and therefore, input and output signals of the functional block are prevented from being analyzed in an unauthorized manner.
A semiconductor apparatus may further include a protection layer, which is formed over the opaque layer, to protect the apparatus. Such a protection film improves the security of the semiconductor apparatus.
The opaque layer may be formed over the enable signal line to cover the enable signal line, so that the security of the semiconductor apparatus is improved. That is, when the opaque layer is removed, the enable signal line is easily broken at the same time. When the enable signal line is broken, the functional block is no longer enabled or activated, and therefore, the functional block is prevented from being analyzed by rogues in an unauthorized manner.
The opaque layer may be formed over the functional block to cover up the functional block, so that it becomes more difficult to analyze the function or operation of the functional block.
The enable signal line may be formed on the same layer as the opaque layer, or may be arranged near the opaque layer, so that the enable signal line would be easily broken at the same time when the opaque layer is removed.
The enable signal line may be connected through a resistance to one of the ground or power supply, so that the functional block is reliably invalidated when the enable signal line is broken. When the enable signal line is broken, a voltage, which is high enough for disabling the functional block, is applied to the functional block; and therefore, the functional block is invalidated.
According to another aspect of the present invention, a semiconductor apparatus further includes a program storage that stores software (program), which invalidates the functional block when at least one of the functional signal line and enable signal line is broken.
According to still another aspect of the present invention, a semiconductor apparatus further includes a circuit that makes a short-circuit between the ground voltage and power supply voltage when at least one of the functional signal line and enable signal line is broken. When one of the functional signal line and enable signal line is broken, a short-circuit is made, so that the semiconductor apparatus itself becomes invalidated and at the same time circuitry around the functional block gets in an error mode. As a result, the semiconductor apparatus is prevented from being analyzed in an unauthorized manner.
According to a further aspect of the present invention, a semiconductor apparatus includes a data storage that stores predetermined data; signal lines which are connected to the data storage; and a program storage that stores software, which invalidates the data, stored in the data storage, when at least one of the signal lines is broken.
According to another aspect of the present invention, a semiconductor apparatus includes a data storage that stores predetermined data; signal lines which are connected to the data storage; and a circuit that makes a short-circuit between the ground voltage and power supply voltage when at least one of the signal lines is broken.